Flutter：如何通过ToggleButtons对ListView进行排序 [英] Flutter: How to sort ListView by ToggleButtons

问题描述

我的列表视图如下：

列表视图的代码：

_listCountry(index) {
  Country country = _country[index];
  return Row(
    mainAxisAlignment: MainAxisAlignment.spaceEvenly,
    children: <Widget> [
      Text('${country.id}'),
      Text(country.name),
      Text('${country.population}'),
    ],
  );
}

我创建了排序方法，效果很好：

And I created methods to sort, it worked fine:

_onSortID() {
  setState(() {
    _country.sort((a, b) => b.id.compareTo(a.id));
  });
}

_onSortName() {
  setState(() {
    _country.sort((a, b) => b.name.compareTo(a.name));
  });
}

_onSortPopulation() {
  setState(() {
    _country.sort((b, a) => b.population.compareTo(a.population));
  });
}

所以我如何将这些方法纳入 ToggleButtons 的按下，以便它们在按下时可以排序？这是切换按钮代码：

So how do I get these methods into the Onpressed of ToggleButtons so that they can sort when pressed? This is the Toggle Button code:

ToggleButtons(
  children: <Widget> [
    Text('Country ID'),
    Text('Country Name'),
    Text('Country Population')
  ],
  onPressed: (int index) {
    setState(() {
      for (int buttonIndex = 0; buttonIndex < isSelected.length; buttonIndex++) {
        if (buttonIndex == index) {
          isSelected[buttonIndex] = !isSelected[buttonIndex];
        } else {
          isSelected[buttonIndex] = false;
        }
      }
    });
  },
  isSelected: isSelected,
)

推荐答案

尝试一下：

定义方法列表

List sortMethods;

然后在 initState（）中创建它，如下所示：

Then create it in initState() like this :

@override
  initState() {
    sortMethods = List.of({
      () => setState(
            () {
              _country.sort((a, b) => b.id.compareTo(a.id));
            },
          ),
      () => setState(() {
            _country.sort((a, b) => b.name.compareTo(a.name));
          }),
      () => setState(() {
            _country.sort((a, b) => b.population.compareTo(a.population));
          })
    });
    super.initState();
  }

当您选择 ToggleButton 时，调用类似

 onPressed: (int index) {
   for (int buttonIndex = 0; buttonIndex < isSelected.length; buttonIndex++) {
        if (buttonIndex == index) {
          isSelected[buttonIndex] = !isSelected[buttonIndex];
        } else {
          isSelected[buttonIndex] = false;
        }
         sortMethods[index]();
      }
     }        

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